Preparation of carboxylated derivatives of long chain unsaturated compounds



United States Patent 3,270,035 PREPARATION OF CARBOXYLATED DERIVA- TIVES OF LONG CHAIN UNSATURATED COMPOUNDS Edward T. Roe, Chalfont, and Daniel Swern, Philadelphia,

Pa., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Original application June 20, 1960, Ser- No. 37,533. Divided and this application Jan. 22, 1962, Ser. No. 176,474

2 Claims. (Cl. 260343.5)

A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This application is a division of Serial No. 37,533, filed June 20, 1960, now abandoned.

This invention relates to carboxylation of long chain unsaturated fatty compounds and has among its objects the carboxylation of long carbon chain olefinic compounds with carbon monoxide at atmospheric pressure.

In accordance with this invention, direct carboxylation of long chain olefinic compounds with carbon monoxide can be achieved at atmospheric pressure by employing a narrow range of operating conditions in which the concentration of the sulfuric acid and also the molar ratio of sulfuric acid to the long chain olefinic compound must be regulated.

According to the present process carbon monoxide at atmospheric pressure is (a) dispersed in aqueous sulfuric acid having a concentration in the range of about 93 to 98% H 80 (b) the olefinic compound is combined with this sulfuric acid at about -20 C. in such proportions that the resulting mixture contains at least about three moles water to each mole of olefinic compound, and (c) during the mixing of olefinic compound and sulfuric acid additional carbon monoxide is dispersed in the mixture. The entire operation is conducted at substantially atmospheric pressure, and the new carboxylic acid derivative is recovered from the sulfuric acid by dilution with water and solvent extraction or mechanical separation.

evident, as shown in Table I, in which the results of the carboxyl-ation of oleic acid are tabulated. In all of these examples the amount of water does not change during carboxylation, since the carbon monoxide is generated externally. The following equation summarzies the chemistry involved:

(wherein x may be 6 to 9).

Commercial oleic acid was purified by crystallization at low temperature followed by fractional distillation to give the oleic acid employed as the starting material in these examples.

The present invention is illustrated with particular reference to Example 6 (Table 1):

Carbon monoxide was passed through 80.4 g. (0.795 mole) of 97.2% sulfuric acid contained in a 500 ml. threeneck flask, vented to the atmosphere, using a gas dispersion tube with a coarse fritted cylinder. With stirring, 7.1 g. (0.025 mole) of oleic acid was added dropwise in 16 minutes to the sulfuric acid solution which was saturated with carbon monoxide. Carbon monoxide was allowed to pass through the stirred mixture for a total of two hours, while the temperature was maintained between 9 and 13 C. with external cooling. At the end of this time the mixture was poured into approximately 300 ml. of a mixture of ice and water. The product was extracted with ether and washed free of sulfuric acid. The ether solution was dried over anhydrous sodium sulfate, filtered, and the ether was then evaporated, yielding 6.4 g. of pale yellow syrupy material having an iodine number, of 12.9, acid number, 300, and saponification number, 300.

The reaction conditions for the other examples were the same as described for Example 6 with the exceptions listed in Table I, specifically, mole ratio of sulfuric acid to oleic acid, concentration of sulfuric acid, and time of stirring the mixture.

TABLE I.REAOTION OF OLEIC ACID WITH GASEOUS CARBON a Water present in sulfuric acid.

b saponification number essentially the same as acid number, except where given below. a saponification number 201.

d saponification number 251.

The product is typically recovered from the reaction mixture by pouring the sulfuric acid solution into a mixture of ice and water, followed by extraction of the product with a suitable solvent such as ether. Alternatively, procedures for extracting the product directly from the reaction mixture may be employed.

A critical variable in the high yield atmospheric carboxylation of the less reactive, long carbon chain nonterminally unsaturated compounds is the concentration and quantity of water. The importance of water is quite Referring to Examples 1 to 8, the extent of carboxylation is indicated by an increase in acid number and a decrease in iodine number. With 91% sulfuric acid (Example 1) no carboxylation takes place. The acid number actually indicates a loss of carboxyl groups. Since the same mole ratio of Water, three moles of Water to one mole of oleic acid, when contained in a more concentrated sulfuric acid (Example 5) is adequate, one must conclude that 91% sulfuric acid is too dilute for this process.

-is extended to six hours.

On the other hand, 1.5 mole of water per mole of oleic acid is insufficient for carboxylation to proceed in a satis- 4 The reduction of the iodine number from that of the starting material also indicates the extent of the reaction.

TABLE II.-OHARACTERISTICS OF CRUDE REACTION PRODUCTS Acid N o. Sapon N o. Iodine No. Percent Hydroxyl Example Starting Yield,

N 0. Material Gms.

Calcd. Found Calcd. Found Calcd. Found Calcd. Found Oleic acid 32 342 297 342 305 2 Oleyl alcohol 33 178 135 178 138 0 5 5. 4 4. 8 Methyl rioinoleate. 29 157 b 217 313 319 0 19 4. 7 l. 4

Linoleic acid 32 344 c 275 344 306 78 48 Yield based on 30 grns. of starting material. b Calculated values are for:

0 Calculated values are for:

factory manner (Examples 2 and 3) even though the concentration of sulfuric acid is 97% and the reaction time With 100 %sulfuric acid (Example 8) carboxylation, if occurring, is negligible, showing conclusively that water must be present during the reaction.

The greatest increase in acid number and decrease in iodine number, indicating maximum carboxylation, is obtained when five moles of water per mole of oleic acid is employed (Example 6). Increasing the amount of water above five moles per mole of oleic acid (Example 7) or increasing the reaction time beyond two hours does not increase the amount of carboxylation.

The product obtained by the carboxylation of oleic acid, the pale yellow viscous liquid described in Example 6, could not be purified by low temperature solvent crystal lization, but distilled readily at about 200 C. and 0.45 mm. mercury pressure to give a product having an acid number of 341, carbon and hydrogen analyses of 69.4 and 11.7%, respectively, and molecular refractivity of 92.8. These and other data obtained for the product are included in Table III. Infrared spectra and gas chromatographic analyses of the product were also obtained. All the data substantiate the conclusion that the product is carboxystearic acid of the Formula I.

CHa-(CHE) r-CH(CH:) (IS-x) C O OH O 0 OH (I) In a major portion of the product, the carboxyl group is probably in the 9 or 10 position (x=7 or 8). How- 'ever, in view of the nature of strong acid-catalyzed double bond addition reactions, the 8 and 11 isomers (x=6 or 9) are also formed.

The source of carbon monoxide may be other than that already illustrated. For example it may be generated in situ by the decomposition of formic acid in the sulfur acid reaction medium, but the composition of the reaction mixture must still adhere to the concentration of sulfuric acid and mole ratio of water to compound to be carboxylated must be approximately as defined by Examples 5 and 6.

Highly purified oleyl alcohol (98-99% methyl ricinoleate and linoleic acid were also carboxylated by the process of the present invention. After pouring the reaction product obtained by carboxylation of oleyl alcohol into an ice and water mixture, it was necesary to hydrolyze the sulfate ester by boiling. Otherwise the procedure was substantially that employed in Example 6.

Table II shows the high recovery of typical crude reaction products and the extent to which they are carboxylated by comparing the acid number of the product with that calculated.

The saponification number of the products obtained from oleic acid and oleyl alcohol are essentially the same as the acid number; with methyl ricinoleate and linoleic acid, however, the saponification number is quite different from the acid number. This suggests that an ester or lactone has formed in the latter two instances. Also, the hydroxyl value of the product obtained from methyl ricinoleate is much lower than would be expected. The significance of these points will be discussed later in more detail.

In all of the preparations except that of the oleic acid derivative, it was desirable to convert the crude reaction products to methyl esters before purification by distillation.

The usual method of direct esterification does not completely esterify the branched carboxyl group. Using dimethyl sulfate, as illustrated in the following example, nearly complete esterification is obtained after 42 hours reflux.

EXAMPLE 13 Preparation of the dimethyl ester of carboxystearic acid carbonate solution in the cold and extracting with ether.

(In larger preparations, from one half to two thirds of the alcohol was distilled olf before neutralization and dilution, thus increasing the efiiciency of the ether extraction.) Distillation of 9.4 grams of the methyl esters from an alembic fiask yielded 5.8 grams of a clear, mobile amber liquid, B.P. 146-148 C. (0.35 mm.), 711330 1.4465. Analysis.Calcd. for C H O C, 70.7; H, 11.3; molar refractivity, 102.8. Found: C, 70.6; H, 11.3; molar refractivity, 102.6.

From the chemical analyses, infrared spectra, and gasliquid chromatography showing several closely related major components it is concluded that the product is a mixture of isomers which would be expected from esterification of the product of Formula I.

Methyl esters of carboxyoctadecanol, carboxylated methyl recinoleate and carboxylated linoleic acid (Examples 15 to 17, respectively) were prepared in a manner similar to that described for esterification of carboxy- Boiling Point Carbon, percent Hydrogen, percent Molecular Ex. Refraction No. Compound m) d 0. mm. Calcd. Found Calcd. Found Calcd. Found 9 Carboxystearie acid 200-201 0. 45 69. 5 69. 4 ll. 1 11. 7 1. 4615 0. 9726 93. 5 92. 8 l3 Dimeithyl ester of earboxystearic 146-148 0.35 70. 7 70. 6 11. 3 l1. 3 1. 4465 0.9281 102. 8 102. 6

am l4- Dibutyl ester of carboxystearic 183-185 0. 40 73.6 73. 4 11. 6 11. 8 1. 4465 0. 9033 130. 6 130. 1

act 15. Methyl ester of carboxyoctadeca- 153-155 0. 45 73. 1 73. 12. 3 12. 3 1.4535 0. 9095 98. 0 97. 7

110 16. Methyl ester of carboxylated 161-162 0. 40 70. 6 69. 2 10. 7 10. 7 1. 4530 0. 9628 96. 0 95. 6

methyl ricinoleate. 17 Mlethyl etsiter 0f carboxylated lino- 160461 0. 40 70. 6 68. 7 10. 7 10.7 1. 4530 0. 9699 96. 0 94. 9

ere aci Percent 0, Percent H and Molecular Refraction calculated for; M X)o1 r(orn)x errcrane 0 0 on,

( +y=9; x probably=1 or 2) EXAMPLE 14 The ester interchange reaction was carried out in the following way. To 33.5 g. of methyl esters (acid number 6.3) prepared from crude carboxystearic acid (acid number 310) was added 142 ml. of n-butanol with which 0.42 g. of metallic sodium had been reacted, and the mixture refluxed for 25 hours. In order to determine when the interchange was complete, the methanol evolved was removed and measured. For this purpose a 1 x fractionating column packed with Raschig rings was used. The product was worked up by pouring the reaction mixture into dilute hydrochloric acid and extracting with ether. After washing the ether layer free of acid it was dried over sodium sulfate, filtered, and the ether was then evaporated, yielding 40.9 g. of crude dibutyl esters having an acid number of 10.7. The acidity of the crude dibutyl esters was neutralized with potassium hydroxide, and the product was vacuum distilled.

The distilled dibutyl esters of carboxystearic acid obtained by the two methods of preparation had the same properties cf. (Table III.)

Neither the methyl or butyl ester could be completely hydrolyzed by refluxing with dilute alcoholic potassium hydroxide for eight hours. This is additional chemical confirmation of a branched carboxylic ester group.

While not illustrated by specific examples it is readily apparent that other esters can be prepared by employing ethanol, propanol, or other higher boiling alkanols in the procedure of Example 14 in place of 'butanol.

The structural similarity among the methyl esters of the carboxylated products was very marked when the infrared spectra were compared. Confirmation of side chain carboxylation is present in all instances, and on the basis of further infrared spectra evidence, carboxylation of oleyl alcohol according to the present invention, followed by esterification, gives a product of the Formula II.

C 0 OR wherein x is 6 to 9 and R is an alkyl group.

The apparent anomaly shown in Tables II and III in respect to the structure of the product obtained by carboxylation of methyl ricinoleate is clarified by study of analytical data and infrared spectra of methyl esters, leading to the conclusion that the crude reaction product is a mixture of wherein the sum of x and y is 9 and x is 1 or 2.

The unsaturation still present in the crude carboxylated linoleic acid is not due to unreacted linoelic acid, as shown by alkaline isomerization. The ultraviolet absorption spectrum of the isomerized and unisome'rized samples are the same. The unsaturation, therefore, must be in 9.11 unsaturated dicarboxylic acid.

A comparison of the chemical and physical data obtained on the distilled methyl esters of carboxylated linoleic acid with those of the distilled methyl esters of carboxylated methyl ricinoleate (Table III) shows a close similarity. The infrared spectra of the two products are essentially identical. The methyl esters of carboxylated methyl ricinoleate and of linoleic acid are, therefore, identical and may be represented by the Formula III o=o (III) wherein the sum of x and y is 9 and x is 1 or 2.

The car-boxylation of long carbon chain olefinic compounds according to the present invention enhances their functional properties for use in the manufacture of alkyd resins, polyesters and polyamides and other polymer applications, or when fully esterified, they can be used as plasticizers or functional fluids such as synthetic lubricants and hydraulic fluids.

We claim:

1. A process comprising dispersing carbon monoxide at substantially atmospheric pressure in sulfuric acid containing about from 2 to 7% water, combining calculated amounts of methyl ricinoleate and said sulfuric acid to provide a liquid phase having a ratio of at least about 3 moles of water to 1 mole of methyl ricinoleate and, at a temperature of about from 10 to 20 C., contacting the methyl ricinoleate in liquid phase with carbon monoxide at substantially atmospheric pressure to introduce a carboxyl group at the double bond, separating derivatives of methyl ricinoleate from the reaction mixture, and distilling said derivatives.

2. A process comprising dispersing carbon monoxide at substantially atmospheric pressure in sulfuric acid containing about from 2 to 7% Water, combining calculated amounts of linoleic acid and said sulfuric acid to provide a liquid phase having a ratio of at least about 3 moles of Water to 1 mole of linoleic acid and, at a temperature of about from 10 to 20 C., contacting the linoleic acid in liquid phase with carbon monoxide at substantially atmospheric pressure to introduce one carboxyl group into the linoleic acid, separating derivatives of linoleic acid from the reaction mixture, esterifying said derivatives with an alkanol, and separating the thus-formed esters from the esterification reaction mixture.

References Cited by the Examiner UNITED STATES PATENTS Bowles 260343.6 Koch 260-413 Nernec 260343.6 Benedictis et a1. 260343.6 Swern et a1. 260-3436 

1. A PROCESS COMPRISING DISPERSING CARBON MONOXIDE AT SUBSTANTIALLY ATMOSPHERIC PRESSURE IN SULFURIC ACID CONTAINING ABOUT FROM 2 TO 7% WATER, COMBINING CALCULATED AMOUNTS OF METHYL RICINOLEATE AND SAID SULFURIC ACID TO PROVIDES A LIQUID PHASE HAVING A RATIO OF AT LEAST ABOUT 3 MOLES OF WATER TO 1 MOLE OF METHYL RICINOLEATE AND, AT A TEMPERATURE OF ABOUT FROM 100 TO 20*C., CONTACTING THE METHYL RICINOLEATE IN LIQUID PHASE WITH CARBON MONOXIDE AT SUBSTANTIALLY ATMOSPHERIC PRESSURE TO INTRODUCE A CARBOXYL GROUP AT THE DOUBLE BAND, SEPARATING DERIVATIVES OF METHYL RICINOLEATE FROM THE REACTION MIXTURE AND DISTILLING SAID DERIVATIVES. 